Authors: Maryam Omidkhoda, Vida Belashnia, Pegah Sadeghnezhad, Neda Eslami
Categories: Research Article, Nasal form, Malocclusion, Lateral cephalogram
Source: The Saudi Dental Journal
Authors: Maryam Omidkhoda, Vida Belashnia, Pegah Sadeghnezhad, Neda Eslami
Considering the significant impact of the nasal form on the appearance of an individual, this study aimed to investigate the relationship between nasal morphology and skeletal malocclusion in a sample of Iranian population. In this descriptive cross-sectional study, 141 lateral cephalograms of individuals of both genders, aged 18 to 30 years were selected. The participants were classified into Class I, II, and III malocclusions. Then, naso-facial landmarks related to the form and shape of the nose and facial skeleton were manually traced on each lateral cephalogram and 13 angular and linear parameters were measured. These parameters were compared among the three types of malocclusions. Statistical analysis of the data was performed using ANOVA, Kruskal–Wallis, and Chi-square tests. P < 0.05 was considered significant. Most of the measurements such as nasal morphology as well as nasal height, nasal bone length, nasal bone angle, nasofrontal angle, dorsum length, total nasal length, nasal depth, columellar convexity, and nasal hump did not show significant differences among different malocclusions (p > 0.05). However, lower dorsum convexity, soft tissue convexity, naso-facial angle, and naso-mental angle were reported to have significant differences among different malocclusions (p < 0.05). According to the results of the present study, the overall shape of the nose is not affected by the type of underlying skeleton in the sample studied. However, future studies with larger sample sizes are recommended to further confirm the results of the present study.
The growth and development of the naso-frontal region, encompassing the morphology and dimensions of the nose, can exert a profound influence on facial aesthetics. Various determinants, including age, gender, culture, ethnicity, and race, play a pivotal role in establishing the ideal standards of aesthetic beauty. It is imperative for plastic surgeons to reconcile socially accepted aesthetic norms with conventional standards of beauty (Krishnaveni 2017).
The development of the nasomaxillary complex constitutes a crucial factor in the overall nasal morphology (Jankowska et al. 2021a, b). The form of the nose undergoes continuous growth until the onset of adolescence, characterized by an annual increase of approximately 1.5 mm in nasal length. This growth is particularly pronounced in the antero-inferior direction (Prasad et al. 2014). Deviations in nasal structure may occasionally arise due to dental anomalies in the maxilla, necessitating meticulous examination of specific parameters (Bhardwaj et al. 2018).
Race and geographical location significantly influence individual appearance, with notable differences observed in nasolabial and naso-frontal angles between Asian populations and their Western counterparts. The position of the upper jaw also has a relationship with the position of the nose (Jankowska et al. 2021a, b). Furthermore, nasal morphology is also influenced by gender. Generally, men exhibit a nose that is more prominent, broader, and taller, whereas women typically possess noses that are narrower, shorter, more concave, and slightly elevated (Aljabaa 2019).
Alterations in nasal prominence, upper lip orientation, and nasolabial angle significantly influence the facial profile and overall aesthetic presentation. Orthodontic practitioners must incorporate the potential for nasal growth into their therapeutic strategies. Nasal growth progresses at a consistent rate and is nearly complete by age 18 in males and 16 in females.
The significance of nasal growth and its subsequent influence on facial aesthetics has garnered increased interest among orthodontic professionals in recent years (Meng et al. 1988). The anatomical proximity of the nose to adjacent tissues underscores its importance in orthodontic treatment planning, with the ultimate objective being the enhancement of patients' quality of life through the improvement of occlusal function and dental aesthetics. While orthodontic interventions do not directly alter the morphology of the nose, the close interrelationship with surrounding tissues accentuates its critical role in achieving favorable treatment outcomes.
According to a recent systematic review (Jankowska et al. 2021b), nasal parameters exhibit significant correlations with skeletal classification, nasolabial angles, the position of the upper incisors, and maxillary inclination (Farkas et al. 1986). Nevertheless, the majority of these investigations have been predominantly conducted within Western populations. Given the ethnic and racial disparities present in the Iranian demographic relative to Western cohorts, it becomes essential to examine the influence of various factors on nasal morphology across different skeletal malocclusions within Iranian populations. To our knowledge, no research has specifically investigated the interrelationship between diverse skeletal parameters and nasal morphology among an Iranian demographic. The objective of this study was to explore the association between nasal morphology and antero-posterior skeletal relationships. To our knowledge, such a study has not previously been conducted within this specific population.
The protocol of this study was approved by the regional ethics committee (Mashhad, Iran). Within the framework of this cross-sectional descriptive research, the lateral cephalometric radiographs of 141 patients aged between 18 to 30 years, who pursued orthodontic intervention at the orthodontic department of Mashhad Dental School (Iran) as well as two private clinics, were meticulously analyzed. This specific age demographic was intentionally chosen due to the significant stabilization of nasal and skeletal growth typically occurring by this period. These subjects had previously acquired initial records, which included lateral cephalograms, as a prerequisite for the commencement of orthodontic treatment. Consequently, no additional financial burden or extra radiation exposure was inflicted upon the patients. Individuals with previous histories of orthodontic or orthognathic interventions, nasal surgical procedures, trauma, or genetic anomalies, including syndromic conditions such as cleft lip and palate, were systematically excluded from the study.
The sample size was estimated to be 45 individuals in each group based on Bhardwaj et al.'s study (2018) considering the mean nasal length of 3.70. ± 49.19, 4.19 ± 51, 4.93 ± 51.77 mm in class I, II, and III, respectively, with ∞ = 95%, and ß = 0.2.
Patients were classified into class I, class II, and class III malocclusion based on their ANB angle. The angle of 1 ≤ ANB ≤ 3 was considered as Class I malocclusion (n = 40), while patients with ANB > 3 and ANB < 1 were classified as Class II (n = 53), and Class III (n = 48) malocclusions, respectively.
Initially, soft and hard tissue landmarks of the nose and maxillofacial regions were manually traced. Tables 1, 2, and Fig. 1 demonstrates the hard and soft tissue landmarks and their definitions. Then, 13 parameters describing the shape and size of the nasomaxillary region including nasal length, nasal depth, and axis of dorsum were recorded. Table 3, and Fig. 2, depicts the different parameters measured on lateral cephalograms. Shape of the nose was further classified into straight, convex, or concave profile according to Table 3, and Fig. 3. All the measurements have been done by the same trained operator to eliminate the potential for inter-observer variability.To assess the intra-observer reliability, the measurements of the lateral cephalogram of 10 patients were repeated by the same operator after one month and the kappa coefficient value was calculated.
Table 1Description of the soft tissue landmarks traced on lateral cephalogramsPrThe most prominent point on the nasal tipAcThe most convex point on the curvature of the nasal alarPcmThe most posterior-inferior point of the nose that connects to the philtrum of the upper lipCmThe most convex point at the junction of columella and lobularLsThe mid‐point of the vermilion line of the upper lipN’The point in the midline of the nasal radix and nasofrontalMnSoft tissue point in the middle of the distance between the points N’ and PrStSoft tissue point halfway between the Midnasale point and the Pronasale pointsSnThe point where the nasal septum merges with the upper cutaneous lip in the mid‐sagittal planePg’The most prominent midline point of the soft tissue chin padG’The most prominent midline point of the forehead between the brow ridgesTable 2Description of the hard tissue landmarks traced on lateral cephalogramsNThe most receding point of the anterior surface of the frontonasal suturePgThe most anterior point on the bony chinRThe most anterior and lowest point at the tip of the nasal boneN1The most receding point of the frontal curvature on the nasal boneN2The most protruding point of the frontal curvature on the nasal boneSCentre of the sella turcicaPoThe uppermost point of the external auditory meatusOrThe lowest point on the lower border of the orbicular cavityAThe most posterior point in the anterior contour of the maxillary alveolusFig. 1Schematic view of the soft and hard tissue landmarks traced manually on lateral cephalogramsTable 3Description of axes (in millimeters) and angles (in degrees) used in the researchAxis of dorsumThe line from the depth of N to StNasal lengthNose distance between Nˊ_PrNasal depthNose vertical distance between Pr and Nˊ-SnNasal heightNose the distance between ˊN and SnNBoneL(Nasal bone length)The line constructed between the N point and the R pointCconv(Columellar convexity)Perpendicular distance between the Pr-Sn line and the most anterior point on the convexity of columellaDconv (Lower dorsum convexity)The line constructed between the N point and the R pointSFC(Soft tissue facial convexity)Convexity of facial soft the angle between Gˊ-Sn and ˊSn-PgThe angle of the nasal bone NBoneA (°)The posterior angle between N1-N2 and N2-RNFA (Nasofacial angle)Nasofacial nasal prominence—the angle between ˊGˊ-Pg and Nˊ_PrNasofrontal angleNaso-frontal the angle between ˊGˊ-N and DNP (dorsal plane of nose Nˊ_Pr)HumpNasal Perpendicular distance between the axis of dorsum and its most prominent soft tissue pointNMA (Nasomental angle)Nasomental the angle between the dorsal axis and ˊPr-PgStraight noseStraight nose tissue tangential to Nˊ_Pr lineConcave noseConcave The nasal tissue is located below the Nˊ_Pr lineConvex noseConvex the upper nasal tissue is located in the Nˊ_Pr lineFig. 2Different nasofacial parameters measured on lateral cephalogramsFig. 3Three types of nasal morphology including straight, concave, and concavex profile
The Shapiro–Wilk test was used to assess the normality of the data. ANOVA and Chi-square tests were used for comparison of the data among the groups. The Kruskal–Wallis test was used to assess the relationship between nasal shape and types of malocclusions.
In this descriptive cross-sectional study, the intra-class correlation coefficient (ICC) was calculated to assess the intra-observer reliability of the measurements. The ICC of all parameters were reported to be higher than 0.7, which is statistically acceptable.
The Chi-Square test was used to compare the frequency of nasal forms in each malocclusion type. According to Table 4, there was not a significant difference in the frequency of different nasal forms among the three malocclusions (p = 0.473). Table 4Correlation between the type of malocclusion and nasal shape Table 4Nasal shapeType of MalocclusionClass I n (%)Class II n (%)Class III n (%)Total n (%)Straight27 (67.5)26 (49.00)25 (52.10)78 (55.3)Convex12 (30)24 (45.3)20 (41.6)56 (39.7)Concave1 (2.5)3 (5.7)3 (6.25)7 (5)Total40 (100)53 (100)48 (100)141 (100)P-value = 0.473
Descriptive data and comparative analysis of the nasal parameters with normal distribution are presented in Table 5. According to the table, ANOVA analysis did not show a statistically significant difference in nasal height, nasal bone height, nasal bone angle, and nasofrontal angle among different types of malocclusions. Table 5Comparative analysis of nasal parameters with normal distribution among different malocclusionsParameterType of malocclusionMeanStd. Deviationp-value*Nasal height (mm)Class I52.534.0190.636Class II52.453.688Class III51.814.251Total52.263.965Nasal bone length(mm)Class I24.654.4120.751Class II24.383.194Class III24.943.605Total24.653.692Angle of the nasal bone (°)Class I165.137.9140.526Class II166.686.679Class III165.885.039Total165.966.552Nasofacial angle (°)Class I134.0711.3710.352Class II134.0411.309Class III136.799.097Total134.9910.630ANOVA
Table 6, depicts the comparative analysis of the measurements with non-parametric distribution. According to this table, there was a statistically significant difference among the different types of malocclusions regarding lower dorsum convexity, soft tissue convexity, nasofacial angle, and nasomental angle. Then, the Kruskal–Wallis test was used for pairwise comparisons between the groups. The analysis showed a significant difference between the Class II and Class III malocclusions in lower dorsum convexity (p = 0.002). Significant differences were also observed in the nasofacial and nasomental angles, as well as the soft tissue convexity among all types of malocclusions (Table 7). Table 6Comparative analysis of nasal measurements with non-parametric distribution among different malocclusionsParameterType of malocclusionMedianInterquartile Rangep-valueAxis of Dorsum (mm)Class I32.0040.210Class II33.003Class III31.503Nasal depth (mm)Class I17.0020.074Class II17.003Class III16.003Columellar convexity (°)Class I3.0010.147Class II3.001Class III3.501Lower dorsum convexity (°)Class I2.0000.006Class II2.000Class III2.001Soft tissue facial convexity (°)Class I165.5060.000Class II160.009Class III171.009Nasofrontal angle (°)Class I32.0040.000Class II34.003Class III29.505Nasal hump (°)Class I132.50150.323Class II132.0016Class III136.5012Nasomental angle (°)Class I129.0060.000Class II1247Class III1327Table 7Pairwise comparison of the studied parameters among the three types of malocclusionsClass I-II P-valueClass I- III P-valueClass II-III P-valueLower dorsal convexity (mm)0.3900.0390.002Soft tissue facial convexity (°)0.0000.0000.000Nasomental angle (°)0.0010.0080.000Nasofrontal angle (°)0.0020.0140.000
Some researchers consider the nose as the keystone of the facial esthetics. The shape of the nose and its relationship with other soft tissue facial structures influence perceived facial attractiveness. According to the results of the present study, the distribution of various nasal forms (straight, convex, and concave) did not show a significant difference in different types of malocclusions. Moreover, among the 13 investigated parameters, only 4 measurements including lower dorsum convexity, soft tissue facial convexity, nasofrontal, and nasomental angles showed a significant relationship with the types of malocclusions.
Sahooet al. (2021) and Jankowska et al. (2021a) conducted a systematic review on different nasal forms in various dentoskeletal patterns. The most prevalent form of the nose was reported to be straight in class I, convex in class II, and concave in class III patients. Similarly, Robisonet al. (1986) found that the most frequent form of the nose in 11 to 20 year old white women with class I, II, and III malocclusions were straight, convex, and concave profiles, respectively. These results are not consistent to ours, which could be due to the different nations and races of the studied population. On the other hand, in line with the current study, Wisthet al. (1975) did not find any correlations between the type of malocclusions and the shape of the nose. They believed that the soft tissue profile is mainly influenced by the position of the chin. (Wisth 1975). Also, in agreement with our findings, Fitzgerald et al*.'s* (Khare and Niwlikar 2017) study showed that there was not a significant relationship between the soft tissue of the nose and the underlying skeleton.
According to Robison et al. (1986) investigation, class I malocclusion patients had the greatest nasofacial angle, while the lowest values were reported in class III malocclusion. In the current study, the nasofacial angle was greater in class II malocclusion and the least amount was observed in class III malocclusion. Different studied population, and age range of their samples (11–20-year-old white women) could contribute to the contradictory results.
We found a significant correlation between nasomental angle and skeletal class. This angle is also related to the upper and lower incisor inclination, maxillary and mandibular positions, as well as to maxillary inclination. Considering more retrognathic position of the chin, and more prognathic maxillary position in class II cases, higher values of nasomental angle in class III, and lower values in class II was expected. This finding was in accordance with some previous studies (Arshad et al. 2013; Gulsen et al. 2006). Moreover, in line with a previous research, we concluded that the convexity of the lower part of the nasal dorsum is strongly dependent on skeletal class (Arshad et al. 2013). Patients with class II malocclusion proved to have a more pronounced convexity in their nose compared to other classes. The angulation of the lower part of the dorsum is closely associated with vertical growth changes of the tip of the nose.
In present study*,* the mean nasal length and nasal depth were found to be 48 mm, and16.6 mm, respectively. These values were comparable to the measurements of Krishnaveni et al. (2017) investigation. They found that the position of the upper jaw can affect the shape of the nose. The mean values for the nasal length and nasal depth in their study group were reported to be 44.4 mm and 16.2 mm, respectively.
Jafarpouret al*.* (2014) investigated nasal morphology and its relationship with malocclusions in Filipino people. The average measured distance of nasal length (Nʹ-Pr) in class I, II, and III malocclusions was reported to be 46.4, 46.9, and 45.6 mm, respectively. These values were comparable to the nasal length measurements of the present study (48.00, 49.00, and 47.00 mm, for class I, II, and III malocclusion, respectively). Also, the nasal height (Nʹ-Sn) was found to be 49.1, 51.2, and, 50.6 mm in class I, II, and III malocclusions, which seemed to be similar to our measurements (51.85, 52.45, and 52.53 mm for class I, II, and III malocclusions, respectively).
The effect of the vertical dimension of the upper jaw on the shape of the nose was studied by Khare and Niwlikar (2017) in 16- to 20-year-old Indian people. They reported that nasal length and nasal depth were significantly different among skeletal malocclusions. This is in contrast to the results of present study. These inconsistent results might be due to the different races of the participants. Moreover, we did not consider the facial vertical dimensions in our study, which might contribute to the different results of these two studies.
According to Gupta et al. (2024), the increased nasal length and depth were observed in patients with an increased lower anterior facial height. However, the nasal parameters were not affected by changes in the upper anterior facial height or growth pattern of the individual.
The patients included in present study were between 18 to 30 years old. According to Meng et al. (1988) at the age of 7, upper nasal height achieved 80% of its final size. Moreover, girls had 90% of their final nasal height already at the age of 7, boys after the age of 17. Nasal depth was 70% of its final measure at the age of 7 in girls, and 11 in boys. Therefore, it seemed that size and shape of the nose was not affected by growth in our participants.
Thorough examination of the nasal form and its relationship with other facial structures should be part of any patient evaluation prior to orthognathic surgery, rhinoplasty, or orthodontic treatment. The form of the nose can also be used to determine age, gender, race, and ethnicity.
Some treatment approaches can change the shape of the nose and thereby the appearance of the face, either directly or indirectly. For example, orthodontic treatment that leads to protrusion of incisors might result in lip alterations that raise the nose's relative prominence. Mandibular surgeries may alter the soft tissue of the chin and lower lip, which may indirectly affect the relative prominence of the nose. On the other hand, maxillary and nasal surgery may directly impact the shape of the nose. During orthodontic treatment, the anterior teeth should be carefully positioned to avoid the nose appearing relatively prominent. In other words, the treatment care must be formulated according to the profile view of an individual. (Rathi et al.) Considering the chance that the nose or other face structures may have been impacted, the study excluded participants with a history of facial surgery, facial fractures, or orthodontic therapy.
There are various methods for measuring different dimensions of the nose, such as lateral cephalometry, computed tomography, stereophotography, and direct clinical measurements. In the current study, lateral cephalometric radiographs were used to evaluate nasal parameters, and also the skeletal malocclusions. Measuring the parameters on two-dimensional radiographs has its own shortcomings including inaccurate tracing of the landmarks due to superimpositions of different facial structures. In order to increase the reliability of landmark identification, one trained operator traced the cephalograms twice within one month interval. The small sample size is another shortcoming of the present study. Due to the limited number of participants in each group, it was not possible for us to further classify the patients according to the vertical dimensions of their facial skeleton.
Future longitudinal studies with larger sample sizes with respect to patients’ age, sex, and facial vertical dimensions on three-dimensional radiographs are strictly recommended to further elucidate the relationship of the nasal shape with the underlying facial skeleton.
There was not a significant difference among the three types of malocclusions in terms of different forms of nasal shape. Most of the nasal measurements did not show significant differences among different malocclusions. A significant difference was found between the class II and class III malocclusions regarding lower dorsum convexity. Significant differences were also observed in the nasofacial and nasomental angles, as well as the soft tissue facial convexity among all types of malocclusions. These differences should be considered during orthodontic treatment planning or orthognathic surgeries as they influence the patients’ soft tissue facial profile as well as occlusion. Orthodontic tooth extraction should be considered in regard to its effect on the prominence of nose and chin soft tissues.